QUICK REFERENCE
- Symbol: Ra
- Atomic Number: 88
- Atomic Weight: 226
- Element Classification: Alkaline Earth Metal
- Discovered By: Marie Curie and Pierre Curie
- Discovery Date: 1898
- Name Origin: From the Latin ‘radius’, meaning ray, in reference to its radioactive properties
- Density(g/cc): 5.5
- Melting Point: 700°C
- Boiling Point: 1737°C
- Appearance: Silvery-white metallic; it is luminescent, turning black when exposed to air
- Atomic Radius(pm): 215
Discovery
Radium was discovered in 1898 by Marie Curie and Pierre Curie during their investigation of pitchblende, a uranium-rich mineral, from which they extracted a new element that exhibited intense radioactivity. The Curies isolated radium as a pure salt, radium chloride, through a painstaking process involving the fractional crystallization of barium and radium compounds due to their chemical similarity. The discovery was a significant milestone in the study of radioactivity, a term coined by Marie Curie.
Relation to Other Elements
Radium is a member of the alkaline earth metals in group 2 of the periodic table, which also includes beryllium, magnesium, calcium, strontium, and barium. Radium shares many chemical properties with its group members, such as forming +2 ions. However, it is distinguished by its radioactivity. All radium isotopes are radioactive, with radium-226 being the most stable isotope, having a half-life of about 1,600 years.
Natural Occurrence
Radium is found in trace amounts in uranium ores such as pitchblende (uraninite) and is extracted as a byproduct of uranium processing. The element is extremely rare in the Earth’s crust. Due to its radioactivity, radium continuously decays, producing radon gas and other decay products.
Uses
Due to its intense radioactivity and scarcity, radium’s uses are limited and have evolved over time:
- Historical Medical Use: In the early 20th century, radium was used in various medical treatments, including cancer therapy, and in luminous paints for dials and instrument panels. However, its use has significantly declined due to the health risks associated with radiation exposure.
- Research: Radium is used in scientific research, particularly in studies of radioactive decay and nuclear physics.
- Radioluminescent Devices: Although less common now, radium was historically used in self-luminous paints for watch dials, instrument panels, and signage. Safer alternatives have largely replaced these applications.
The discovery of radium by the Curies was instrumental in the development of nuclear physics and chemistry, contributing to our understanding of radioactive elements and their properties. While the practical uses of radium are limited by its radioactivity and health risks, its historical significance remains a landmark in scientific discovery.